ELI5: Explain Like I'm 5

Inverse Wishart distribution

The inverse Wishart distribution is like a special recipe for making random matrices, but it's not exactly a recipe for making cookies or pizza dough. Instead, it's a recipe for making matrices that are used in things like statistics and math.

First, let's talk about matrices. A matrix is like a grid of numbers. It has rows and columns, and each number is called an element. Matrices are used to represent things like measurements or vectors (which are like arrows in space).

Now, let's talk about the Wishart distribution. This is a type of distribution (a way of describing the likelihood of certain values) that is used in statistics. Specifically, it describes the distribution of matrices that result from multiplying a set of random vectors together.

Finally, the inverse Wishart distribution is like an "opposite" version of the Wishart distribution. Instead of describing the distribution of matrices that result from multiplying random vectors together, it describes the distribution of the *inverse* of those matrices.

This might sound complicated, but think of it this way: imagine you have a recipe for making pizza dough. The Wishart distribution is like a recipe for making different types of pizza using that dough. But the inverse Wishart distribution is like a recipe for making the dough itself, but in *reverse*. You start with the finished pizza (which is the matrix resulting from multiplying random vectors together), and then the inverse Wishart distribution explains the likelihood of different *doughs* that could have been used to make that pizza.

So, to sum up: the inverse Wishart distribution is a way of describing the likelihood of different types of matrices that could have been used to create a matrix resulting from multiplying random vectors together. It's like a recipe for making the "dough" that was used to make the "pizza" (or the matrix).